Snus Effect on Newborn Birth Weight: Very Small

Three years ago I discussed several Swedish studies reporting that pregnant women who use snus are at risk for (1) slightly smaller babies and premature delivery and preeclampsia (here); and (2) premature birth and stillbirth (here).  Although the risks were lower than those from smoking, I advised that “pregnant women should refrain from using all tobacco products.” 

A new Swedish study confirms that the effect of snus use on birth weight is small, but the researchers made a gross oversight in their journal article.

The new study was conducted at Lund University and was based on over 900,000 births chronicled in the Swedish Birth Registry from 2002 to 2010.  It looked at the effect of snus use on birth weight with a conventional analysis and with a special analysis in which mothers had used or not used snus during two different pregnancies (a “sibling analysis”).    

Conventional analysis found that snus users’ babies weighed a statistically significant 47 grams (about 1.7 ounces) less than those of never users.  This is approximately the same magnitude found in the earlier study I discussed (here).  However, there was only a 20 gram reduction in the sibling analysis, which was not significant. 

The Lund authors emphasize: “Our findings should not be interpreted as suggesting that the use of snus is a healthier alternative to smoking during pregnancy…”  This might be an appropriate statement, but for the fact that the researchers report no attempt to compare and analyze the data they held on the births experienced by more than 100,000 smokers.

Exaggerating small risks but failing to directly compare smokeless tobacco users with smokers seems to be endemic among many scientists with anti-tobacco leanings.  Datasets from the Karolinska Institute and the American Cancer Society contain risk information for both smokeless users and smokers, but staff at these organizations refuse to report comparable risks for these two groups.

The Lund University study appears in PLoS (Public Library of Science) One (here).  The publisher banned studies funded by the tobacco industry, a policy I labeled as unscientific three years ago (here).

Weight! Quit Smoking Without the Gain

It is well established in the scientific literature that smokers generally weigh less than nonsmokers, and that smokers who quit are at risk for weight gain. A recent article in the journal Science (abstract here) reported that nicotine activates specific nerve cells in the section of the brain called the hypothalamus. This interaction may be responsible for decreased appetite; it is different from nicotine’s trigger of reward and satisfaction in the brain. This complex research was conducted in mice, so the results will need confirmation in human studies. Still, they substantiate two dreaded downsides to quitting smoking: the loss of the powerfully rewarding and satisfying activity, and the gain of unwanted pounds.

We already know that switching from cigarettes to smokeless tobacco keeps smokers satisfied while giving them almost all of the benefits of complete tobacco/nicotine abstinence. But does switching keep the weight off?

In 2004, I published the first and only research article answering this question (abstract here). Along with colleagues from Umeå University in Sweden, I used a World Health Organization dataset to evaluate weight gain among nearly 3,000 men in Northern Sweden.

Weight Gain Over Nine Years Among Men in Northern Sweden
Tobacco Category	Average (lbs)
Nonusers (Referent group)	7.0
Smokers	5.1
Smokers who quit completely	15.0*
Smokers who switched to snus	7.9
Snus users	6.8
Snus users who quit completely	11.2*
*significantly elevated compared with nonusers

The big gainers were smokers and snus users who became completely abstinent from nicotine and tobacco. But snus users and smokers who switched to snus didn’t gain any more weight than nonusers. This is important news for smokers who are concerned about putting on pounds when attempting to quit smoking.

I also noted that the rate of overweight at the start of the study was 32% among those who didn’t use tobacco, 29% among smokers, and 42% for ex-smokers. These percentages are somewhat lower than other reports because our group defined overweight as a body mass index (BMI) of 27 or higher. The standard definition of overweight starts at a BMI of 25. For more information about BMI, go to this website at the federal National Heart Lung and Blood Institute.

Fear of gaining weight should not deter smokers from quitting. Research shows that a switch to smoke-free tobacco can leave them healthier with no added pounds.

Tobacco Harm Reduction: Not During Pregnancy

One of the most common – and challenging – questions regarding tobacco harm reduction is whether it is applicable to pregnant women who smoke.

According to the 2004 Surgeon General’s report, smoking during pregnancy is associated with increased risks for premature delivery, low-birth-weight infants, and stillbirth. Smoking is also associated with increased risk for problems with the placenta (the organ that nourishes the fetus). These problems include growth of the placenta in the wrong location (placenta previa) and separation of the placenta from the mother’s uterus (placental abruption), both of which can place the mother and developing fetus at risk. Paradoxically, pregnant women who smoke have a significantly lower risk of preeclampsia (a form of high blood pressure). But the overall effect of smoking on the developing fetus is decidedly negative.

Can a pregnant smoker who switches to smokeless tobacco benefit her health and that of her developing baby? Only one scientific study has addressed this issue. It reported information on pregnancy outcomes among Swedish women who used snus or smoked, compared with nonusers of tobacco, and it was published in 2003 by a group of investigators from the Karolinska Institute in Sweden and the National Institute of Child Health and Human Development in the U.S. The abstract is available here.

In this study, tobacco users had smaller babies than nonusers, although the reductions were modest. The average baby weight for nonusers was 7 pounds 14 ounces; babies of snus users weighed 7 pounds 13 ounces, while light smokers (1-9 cigarettes per day) and heavier smokers (10+ cigarettes) had babies that weighed less (7 pounds 8 ounces and 7 pounds 6 ounces, respectively).

Women who used snus were more likely than nonusers to have a premature delivery (adjusted odds ratio, aOR = 1.79, 95% confidence interval = 1.27 – 2.52), which was similar to that of light (aOR = 1.56, CI = 1.33 – 1.83) and heavier smokers (aOR = 1.84, CI = 1.53 – 2.21).

This study confirmed that smoking is protective for preeclampsia. The aOR for light smokers was 0.71 (CI = 0.59 – 0.88), and heavier smokers’ risk was even less (aOR = 0.48, CI = 0.36 – 0.64). However, snus users had a somewhat elevated risk for preeclampsia (aOR = 1.58, CI = 1.09 – 2.27).

In summary, pregnant women who use snus are at risk for slightly smaller babies, and they also have modestly elevated risks for premature delivery and preeclampsia. Women who are pregnant should refrain from using all tobacco products.

Note: The original link to the research study abstract was wrong. It was corrected on September 7, 2010.